Title:
Heat transferring member and heat exchanger having the same
Kind Code:
A1


Abstract:
A heat transferring member has a base wall including a base portion and angled portions. The angled portions extend from opposite sides of the base portion with respect to a flow direction of a fluid. The angled portions are provided by portions that are cut out from the base wall on opposite sides of the base portion and bent relative to the base wall.



Inventors:
Asano, Kazue (Kariya-city, JP)
Itoh, Akira (Kariya-city, JP)
Shimoya, Masahiro (Kariya-city, JP)
Genda, Hiroyuki (Kariya-city, JP)
Application Number:
11/732476
Publication Date:
10/11/2007
Filing Date:
04/03/2007
Assignee:
DENSO Corporation (Kariya-city, JP)
Primary Class:
International Classes:
F28D1/02
View Patent Images:



Primary Examiner:
LEO, LEONARD R
Attorney, Agent or Firm:
HARNESS DICKEY (TROY) (Troy, MI, US)
Claims:
What is claimed is:

1. A heat transferring member for transferring heat with a fluid, comprising: a base wall including a base portion; a first angled portion; and a second angled portion, wherein the first angled portion and the second angled portion extend from opposite sides of the base portion and are angled relative to the base wall, and the first angled portion, the second angle portion and the base portion provide a heat exchanging part.

2. The heat transferring member according to claim 1, wherein the heat exchanging part is one of a plurality of heat exchanging parts.

3. The heat transferring member according to claim 2, wherein the first angled portions and the second angled portions of the plurality of heat exchanging parts have substantially equal dimension with respect to a direction perpendicular to the base wall.

4. The heat transferring member according to claim 2, wherein the plurality of heat exchanging parts is arranged with respect to a flow direction of the fluid such that the first angled portions are located upstream of the base portions and the second angled portions are located downstream of the base portions with respect to the flow direction of the fluid, and some of the plurality of heat exchanging parts are disposed upstream of a reference point of the base wall, and the first angled portions of the some of the plurality of heat exchanging parts have dimensions greater than dimensions of the second angled portions thereof with respect to a direction perpendicular to the base wall.

5. The heat transferring member according to claim 2, wherein the plurality of heat exchanging parts is arranged with respect to a flow direction of the fluid, the plurality of heat exchanging parts includes upstream heat exchanging parts and downstream heat exchanging parts, the upstream heat exchanging parts are disposed upstream of a reference point of the base wall and the downstream heat exchanging parts are disposed downstream of the reference point with respect to the flow direction of the fluid, and the upstream heat exchanging parts have dimensions greater than dimensions of the downstream heat exchanging parts with respect to a direction perpendicular to the base wall.

6. The heat transferring member according to claim 1, wherein at least one of the first and second angled portions is right-angled relative to a surface of the base portion.

7. The heat transferring member according to claim 1, wherein each of the first and second angled portions is angled in a range between at least 40° and at most 140° relative to a surface of the base wall.

8. The heat transferring member according to claim 1, wherein the heat exchanging part is one of a plurality of heat exchanging parts, and the plurality of heat exchanging parts are arranged in a row and has symmetric relationship with respect to a reference point of the base wall.

9. The heat transferring member according to claim 1, wherein the heat exchanging part defines a height in a direction perpendicular to the base wall and a width in a direction along the base portion and perpendicular to the first and second angled portions, and a ratio of the height to the width is in a range between at least 0.9 and at most 1.25.

10. The heat transferring member according to claim 9, wherein the ratio is in a range between at least 0.95 and at most 1.2.

11. The heat transferring member according to claim 10, wherein the ratio is in a range between at least 1.0 and at most 1.15.

12. The heat transferring member according to claim 1, wherein the heat exchanging part is one of a plurality of heat exchanging parts arranged in a flow direction of the fluid at a predetermined pitch, and each of the plurality of heat exchanging parts has a dimension, in a direction perpendicular to the base wall, in a range between at least 0.02 mm and at most 0.4 mm, and the predetermined pitch is in a range between at least 0.04 mm and at most 0.75 mm.

13. The heat transferring member according to claim 12, wherein the dimension of the heat exchanging part is in a range between at least 0.1 mm and at most 0.35 mm, and the predetermined pitch is in a range between at least 0.2 mm and at most 0.7 mm.

14. The heat exchanging member according to claim 13, wherein the dimension of the heat exchanging part is in a range between at least 0.2 mm and at most 0.3 mm, and the predetermined pitch is in a range between at least 0.4 mm and at most 0.6 mm.

15. A heat exchanger comprising: a tube defining a passage for allowing a heat medium to flow therein; and a fin disposed on an outer surface of the tube, wherein the fin includes the heat transferring member according to claim 1.

16. The heat exchanger according to claim 15, wherein the fin has a thickness in a range between at least 0.01 mm and at most 0.1 mm.

17. The heat exchanger according to claim 15, wherein the fin has a corrugated shape.

18. The heat exchanger according to claim 15, wherein the fn includes the heat transferring member according to claim 3.

19. The heat exchanger according to claim 15, wherein the heat medium is a refrigerant.

Description:

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-103878 filed on Apr. 5, 2006, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a heat exchanging member and a heat exchanger having the same.

BACKGROUND OF THE INVENTION

A heat exchanger having fins formed with louvers for improving efficiency of heat exchange is known. For example, in a heat exchanger disclosed in Japanese Unexamined Patent Publication 2005-121348 (US 2004/0206484 A1), a fin has angled pieces on its flat plate part. The angled pieces are cut and angled from the flat plate part. In other words, the angled pieces extend from base portions of the flat plate part and have L-shaped cross-sections with the base portions. In this heat exchanger, a flow of air is disturbed by the angled pieces. Thus, coefficient of heat transfer between the air and the fins increases, and hence the efficiency of heat exchange improves.

Each of the angled pieces is formed on one side of each base portion. Thus, in bending the angled pieces from the flat plate part, the base portions receive moment in one direction. As a result, boundaries between the angled pieces and the base portions will be distorted or twisted. Further, since the flat plate part has plural angled pieces, the flat plate part will be deformed entirely. Therefore, it is difficult to stably provide the fins with predetermined shapes.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter, and it is an object of the present invention to provide a heat transferring member having a shape to be stably formed.

It is another object of the present invention to provide a heat transferring member having a shape capable of improving productivity and a heat exchanger having the heat transferring member.

According to an aspect of the present invention, a heat transferring member has a base wall including a base portion, a first angled portion and a second angled portion extending from opposite sides of the base portion. The first angled portion, the second angled portion and the base portion provide a heat exchanging parts.

The first and second angled portions are formed by cutting portions of the base wall on the opposite sides of the base portion and bending the portions relative to the base wall. Since the first and second angled portions are bent on the opposite sides of the base portion, moments are exerted to the base portion in directions for canceling to each other while bending the first and second angled portions.

Therefore, it is less likely that boundaries between the first and second angled portions and the base portion will be twisted. As such, accuracy of forming the angled portions improves. Accordingly, the heat transferring members having a desired shape are stably produced. Further, productivity of the heat transferring member improves. The heat transferring member is employed to a fin of a heat exchanger, for example.

The heat transferring member can have a plurality of heat exchanging parts. The heat transferring parts are arranged in a flow direction of a fluid such that the first angled piece of each heat transferring part is disposed on an upstream side of the corresponding base portion and the second angled piece of the heat transferring part is disposed on a downstream side of the corresponding base portion with respect to the flow direction of the fluid.

For example, the first angled pieces and the second angled pieces of the heat transferring parts can have the substantially same dimension with respect to a direction perpendicular to the base wall. In this case, the amount of moments caused while bending the first and second angled portions are substantially equally exerted to the base portions. Thus, the base portions are restricted from being twisted when the first and second angled portions are bent.

Alternatively, the first angled portion and the second angled portion can have different dimensions with respect to a direction perpendicular to the base wall. For example, in some of the heat exchanging parts, which are located upstream of a reference point, the first angled pieces have the dimensions greater than the dimensions of the second angled pieces thereof. In this case, the flow of air is further disturbed in an upstream area of the base wall. As such, coefficient of heat transfer improves. Further, an increase of pressure loss (resistance to flow) due to excess disturbance of the air will be reduced in a downstream area of the base wall.

Instead, the dimensions of some of the heat exchanging parts that are located upstream of a reference point of the base wall can be greater than the dimensions of the heat exchanging parts that are located downstream of the reference point. Also in this case, the flow of air is effectively disturbed in the upstream area of the base wall, and the coefficient of heat transfer improves. Further, the increase of pressure loss due to the excess disturbance of the air will be reduced in the downstream area of the base wall.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 is a front view of a heat exchanger according to a first embodiment of the present invention;

FIG. 2 is a perspective view of a fin of the heat exchanger according to the first embodiment;

FIG. 3 is a perspective view of a part of the fin according to the first embodiment;

FIG. 4 is a cross-sectional view of the fin taken along a line IV-IV in FIG. 2;

FIG. 5 is an enlarged cross-sectional view of louvers of the fin shown in FIG. 4;

FIG. 6 is a schematic diagram of a roller forming apparatus according to the first embodiment;

FIG. 7 is a graph of a simulation result for showing a relationship between an arrangement pitch of the louvers and efficiency of heat exchange according to the first embodiment;

FIG. 8 is a graph of a simulation result for showing a relationship between height H of angled pieces of the fin and efficiency of heat exchange according to the first embodiment;

FIG. 9 is a cross-sectional view of upstream louvers of a fin according to second and third embodiments of the present invention;

FIG. 10 is a cross-sectional view of louvers of a fin according to a fourth embodiment of the present invention;

FIG. 11 is a graph showing a relationship between a ratio H1/L of height H1 of an upstream angled piece to width L of a base piece of the fin and efficiency of heat exchange according to the fourth embodiment;

FIG. 12 is a graph showing a relationship between the ratio H1/L and pressure loss according a fifth embodiment of the present invention;

FIGS. 13A to 13C are cross-sectional views for showing examples of shapes of louvers of a fin according to a fifth embodiment of the present invention; and

FIGS. 14A to 14C are cross-sectional views for showing examples of shapes of louvers of a fin according to the fifth embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

A first embodiment will be described with reference to FIGS. 1 to 8. In the first embodiment, a heat exchanger shown in FIG. 1 is for example employed as a radiator for a vehicle air conditioner.

For example, the radiator is a high pressure side heat exchanger of a vapor compression type refrigerating cycle, and radiates heat of a refrigerant discharged from a compressor of the vapor compression type refrigerating cycle. The radiator is also referred to as a refrigerant condenser. In a refrigerating cycle using carbon dioxide and the like as a refrigerant, when the refrigerant discharged from a compressor has a pressure lower than a critical pressure, the refrigerant is condensed in the radiator by radiating heat absorbed in an evaporator. On the other hand, when the refrigerant discharged from the compressor has a pressure equal to or greater than a critical pressure, the refrigerant is cooled without condensing in the radiator by radiating heat absorbed in the evaporator.

As shown in FIG. 1, the radiator has a core part as a heat exchanging part, header tanks 3, and side plates (inserts) 4. The core part includes tubes 1 and fins 2 as heat transferring members. The tubes 1 define passages through which a refrigerant flows. The fins 2 are joined to outer surfaces of the tubes for increasing a heat transferring area with air, thereby to facilitate heat exchange between the air and the refrigerant.

The header tanks 3 are arranged at the longitudinal ends of the tubes 1 and extend in a direction perpendicular to a longitudinal direction of the tubes 1. The header tanks 3 are in communication with the tubes 1. The side plates 4 are arranged at ends of the core part as reinforcement member for reinforcing the core part.

The radiator further has a refrigerant inlet on one of the header tanks 3 and a refrigerant outlet on the other one of the header tanks 3. Alternatively, the radiator may have the refrigerant inlet and the refrigerant outlet on the same header tank 3. In the latter case, the remaining header tank 3 is provided with a separator(s) so that the refrigerant flows in U-turn or serpentine manner in the radiator.

For example, the preceding components such as the tubes 1, fins 2, header tanks 3, and side plates 4 are made of metal such as aluminum alloy. Also, the preceding components are integrally joined such as by brazing.

The fin 2 is a corrugated fin including plate sections 2a and end sections 2b positioning the adjacent plate sections 2a at predetermined intervals. Each of the plate sections 2a has a plate shape and provides surfaces extending along a flow direction A1 of the air as an external fluid. The plate section 2a is for example a flat plate. Thus, the plate section 2a is also referred to as a flat plate section 2a, hereafter.

Each of the end sections 2b for example has a flat plate shape having a width smaller than that of the flat section 2a. The end section 2b provides an outer surface joined with the outer surface (flat walls) of the tube 1 such that heat is transferred between them. As shown in FIG. 2, the plate section 2a and the end section 2b are perpendicular to each other and define a right angled corner between them.

The width of the end section 2b is very small. If the corners between the end section 2b and the adjacent plate sections 2a define a radius, the end section 2b can be recognized as a curved or bend portion overall. Thus, the end section 2b is also referred to as a curved section 2b. In this embodiment, the corrugated fin 2 is for example formed from a thin metal sheet by roll forming.

As shown in FIG. 4, the flat section 2a of the fin 2 has angled pieces 2c. The angled pieces 2c are formed by cutting portions of the flat section 2a and moving or bending the cut portions relative to the remaining portion of the flat section 2a such that the cut portions make right angles with the flat section 2a. Thus, the flat section 2a has openings as slits. Each angled piece 2c has a height so that it is realized to extend from the flat section 2a, which defines a base wall of the fin 2.

Here, the height of the angled piece 2c corresponds to a dimension in an up and down direction in FIGS. 3 and 4. This height of the angled piece 2c is also referred to as a width of the angled piece 2c. The angled pieces 2c have the same height. One opening is formed by making a H-shaped cut on the flat section 2a and moving opposite portions of the cut relative to the flat section 2a as opening. Thus, two angled pieces 2c are formed on opposite sides of one opening. The two angled pieces 2c of one opening belong to different louvers (heat exchanging parts) 20, which will be described later. Also, a total height of the two angled pieces 2c is equal to a width of the opening.

Each of the angled pieces 2c has a rectangular shape having longitudinal sides in a direction along a direction in which a height of the fin 2 is measured. The angled piece 2c has a shape as a belt. Here, the height of the fin 2 is measured in an up and down direction in FIG. 1. The angled piece 2c extends in a direction intersecting with an air flow direction A1 in FIG. 2. In this embodiment, the angled piece 2c extends in a direction parallel to the direction in which the height of the fin 2 is measured and in a direction perpendicular to the air flow direction A1.

Also, the length of the angled piece 2c is substantially equal to the height of the fin 2. That is, the angled piece 2c has a first end at a position adjacent to one end section 2b and a second end at a position adjacent to the opposite end section 2b of the flat section 2a. Thus, the opening defined between the two angled pieces 2c has a length substantially equal to the height of the fin 2.

In this embodiment, the angled piece 2c is right-angled relative to the flat section 2a. The right-angle includes approximately 90°.

In this fin 2, the air collides with the angled pieces 2c while flowing along the surface, of the flat section 2a. Thus, the flow of air is disturbed so as to increase a coefficient of heat transfer between the fin 2 and the air. Accordingly, the angled pieces 2c serve as collision walls for disturbing the flow of the air.

Referring to FIGS. 2 and 3, portions of the flat section 2a located between the openings are referred to as base portions (base pieces) 2d. The base portion 2d continuously extends to two angled pieces 2c with respect to the air flow direction A1.

In this embodiment, the two angled pieces 2c, which extend from opposite sides of the base portion 2d, are bent on the same side of the flat section 2a. That is, the two angled pieces 2c are formed on the same surface of the flat section 2a. Further, the two angled pieces 2c extend parallel to each other. Specifically, in FIG. 3, a right angled piece 2c, which is located on a right side of one base piece 2d is moved from the flat section 2a in a counterclockwise direction, and a left angled piece 2c, which is located on a left side of the base piece 2d is moved from the flat section 2a in a clockwise direction.

As such, the base piece 2d and the two angled pieces 2c located on both sides of the base piece 2d have a substantially U-shaped cross-section or a cross-section as a bracket, as shown in FIG. 5. Hereafter, this U-shaped portion including the base piece 2d and the two angled pieces 2c extending from the base piece 2d is referred to as the louver 20. In this embodiment, all the angled pieces 2c of one flat section 2a extend in the same direction.

Also, the angled pieces 2c of one flat section 2a have the same length, and the ends of the angled pieces 2c are aligned in a longitudinal direction of the flat section 2a, i.e., in the air flow direction A1. Thus, the strength of the flat section 2a improves at both the sides thereof. As such, the strength of the flat section 2a is greater than that of the end section 2b, which does not have the angled pieces 2c. Thus, the end section 2b can be sharply bent relative to the flat section 2a.

The flat section 2a has plural louvers 20. The louvers 20 are parallel to each other and arranged in the air flow direction A1 such that the air sequentially collides with the louvers 20. As shown in FIG. 4, the louvers 20 are arranged symmetric with respect to a reference point C that is located at a predetermined position with respect to the air flow direction A1.

In this embodiment, the reference point C is located in a substantially middle position with respect to the air flow direction A1. The number of the angled pieces 2c that are located upstream from the reference point C is equal to the number of the angled pieces 2c that are located downstream from the reference point C. Also, all the angled pieces 2c have the same height (hereafter, referred to as angled piece height H). In FIG. 4, Gr1 denotes a group of upstream louvers 20 and Gr2 denotes a group of downstream louvers 20.

In the above discussion, it is described that two angled pieces 2c are formed on both sides of each base piece 2d. The flat section 2a has two end walls at its upstream end and downstream end with respect to the air flow direction A1, and a middle wall at the middle position. The ends walls and the middle wall are flat and wider than each base piece 2d with respect to the air flow direction A1. The end walls and the middle wall also have angled pieces having the same shape as the angled pieces 2c extending from the base pieces 2d.

Considering the above, it can be seen that the angled pieces 2c are formed on both sides of the respective openings. That is, all the openings have the angled pieces 2c on both sides. In other words, each base piece 2d has the two angled pieces 2c extending in the same direction on its both sides, irrespective of the width of the base piece 2d.

Next, a structure of a roller forming apparatus for forming the fin 2 will be described with reference to FIG. 6. As shown in FIG. 6, the roller forming apparatus generally includes a tensioning unit 12, a forming roller unit 13, a cutting unit 14, a feeding unit 15, reforming unit 16, a brake unit 17 and the like.

The tensioning unit 12 applies predetermined tension force to a fin material 11, which has a thin plate shape and drawn from a material roll (un-coiler) 10. The tensioning unit 12 has a weight tension part 12a for applying predetermined tension to the fin material 11 by gravity, a roller 12b rotatable with movement of the fin material 11 and a roller tension part 12d that includes a spring part 12c for applying predetermined tension to the fin material 11 through the roller 12b. Here, the predetermined tension force is applied to the fin material 11 in order to maintain the height of the fin, which is bent in the fin forming unit 13, in a constant level.

The fin forming unit 13 bends the fin material 11 into a corrugated shape to have the curved sections 2b and the flat sections 2a and forms the angled pieces 2c on portions corresponding to the flat sections 2a. The fin forming unit 13 includes a pair of forming rollers 13a. The rollers 13a have gear shapes including teeth 13b. The rollers 13a have cutters (not shown) on the teeth 13b for forming the angled portions 2c. The fin material 11 is bent into the corrugated shape along the teeth 13b and the angled pieces 2c are formed while being carried between the pair of rollers 13a.

The cutting unit 14 cuts the fin material 11 into a predetermined length such that one fin 12 has a predetermined number of the curved sections 2b. The fin material 11, which has been cut in the predetermined length, is fed toward the reforming unit 16 by the carrying unit 15.

The carrying unit 15 has a pair of rollers 15a. The pair of rollers 15a are gears having teeth that are arranged at reference intervals (pitch) substantially equal to the intervals of the adjacent curved sections 2b formed in the fin forming unit 13. Here, the intervals between the adjacent curved sections 2b of the corrugated fin 2 are generally referred to as a fin pitch Pf. The fin pitch Pf is twice of a distance between the adjacent flat sections 2a, as shown in FIG. 4.

As an angle of pressure of the forming rollers 13a is increased, the fin pitch Pf of the fin 2 in the finished condition is reduced. On the other hand, as the angle of pressure of the forming rollers 13a is reduced, the fin pitch Pf of the fin 2 in the finished condition is increased. In a case that difference of modules of the forming rollers 13a and the carrying rollers 15a is within 10%, the fins are formed without replacing the carrying rollers 15a.

The reforming unit 16 reforms the undulation of the curved sections 2b by pressing the curved sections 2b in a direction substantially perpendicular to the ridge of the curved sections 2b. The reforming unit 16 includes a pair of reforming rollers 16a, 16b. The reforming rollers 16a, 16b are arranged on opposite sides of the fin material 11 and rotatable in accordance with the movement of the fin material 11. Further, the reforming rollers 16a, 16b are arranged such that a line passing through rotation axes of the reforming rollers 16a, 16b is perpendicular to a feeding direction of the fin material 11.

The brake unit 17 includes a brake shoe 17c having a brake surface 17a and a plate member 17e having a brake surface 17b. The brake unit 17 is located downstream from the reforming unit 16 with respect to a feeding direction of the fin material 11. The brake unit 17 compresses the fin material 11 by a feeding force generated by the carrying unit 15 and friction generated by the brake surfaces 17a, 17b such that the curved sections 2b are in contact with each other.

Here, an end of the brake shoe 17c is rotatably supported, and a spring member 17d is provided on the other end of the brake shoe 17c, as a friction controlling device. Thus, the friction generated by the brake surfaces 17a, 17b is controlled by controlling deflection of the spring member 17d. The plate member 17e is made of a material having sufficient resistance to wear, such as dies steel.

Next, an operation of the roller forming apparatus will be described. First, the fin material 11 is drawn from the material roll 10 (drawing step). Then, the predetermined tension is applied to the fin material 11 in the feeding direction of the fin material 11 in the tensioning unit 12 (tensioning step). Next, the curved sections 2b and the angled pieces 2c are formed on the fin material 11 (fin forming step). The formed fin material 11 is cut in a predetermined length in the cutting unit 14 (cutting step).

The fin material 11 having the predetermined length is carried toward the reforming unit 16 by the carrying unit 15 (carrying step). Then, in the reforming unit 16, the curved sections 2b are pressed so as to reform the duration of the fin material 11 (reforming step). Further, the fin material 11 is contracted such that the adjacent curved sections 2b are in contact with each other in the brake unit 17 (contracting step).

After the contracting step, the fin material 11 expands by its resiliency and has a predetermined fin pitch Pf. Then, checking such as dimensional inspection is performed. In this way, the corrugated fins 2 are produced.

In this embodiment, the angled pieces 2c are formed on both sides of the base pieces 2d and extend in the same direction. Therefore, when the angled pieces 2c are formed, moments are exerted to the base piece 2d in directions for canceling with each other. As such, it is less likely that a boundary between the base piece 2d and the angled piece 2c, i.e., a base of the angle piece 2c, will be distorted. Accordingly, accuracy of forming the louvers 20 improves. As a result, the louvers 20 are properly formed into the desired shapes and productivity of the fins 2 improves.

In this embodiment, all the louvers 20 have the substantially same height H. Therefore, in each base piece 2d, moment caused when bending the angled piece 2c on its upstream side and moment caused when bending the angled pieces 2c on its downstream side are substantially equal. As such, the bases of the angled pieces 2c are restricted from being distorted while bending the angled pieces 2c effectively. Accordingly, accuracy of forming the angled pieces 2c further improves. With this, productivity of the fins 2 further improves.

Further, the louvers 20 are arranged symmetrically with respect to the reference point C. In the fin forming step, bending forces are continuously exerted to the fin material 11 in directions for canceling to each other. Therefore, it is less likely that the fin material 11 will be deformed such that it is biased and collected in one direction when the angled pieces 2c are formed. Because the base pieces 2d and the angled pieces 2c are stably formed, the productivity of the fins 2 further improves.

Also, the louvers 20 are formed by bending the angled pieces 2c on both sides of the base piece 2d with respect to the air flow direction A1. The louvers 20 are formed at predetermined intervals without cutting out or wasting the fin material 11. Therefore, a yield rate of the fin material 11 improves.

In addition, since the angled pieces 2c are formed on both sides of the base piece 2d, distances between the adjacent louvers 20 are increased without excessively increasing the angled piece height H. Thus, an effect of enhancing disturbance of the air is improved while suppressing an increase of pressure loss (resistance to flow of the air). With this, the coefficient of heat transfer improves. Accordingly, the efficiency of heat exchange improves.

According to an examination, it is preferable that the fin 2 has a thickness in a range between equal to or greater than 0.01 mm and equal to or less than 0.1 mm. FIG. 7 shows a simulated result of the efficiency of heat exchange relative to a louver pitch P of the louvers 20. FIG. 8 shows a simulated result of the efficiency of heat exchange relative to the angled piece height H.

The louver pitch P is an interval between the adjacent louvers 20 with respect to the air flow direction A1, as shown in FIG. 5. The angled piece height H corresponds to a dimension (height) of the louver 20 in a direction perpendicular to the air flow direction A1. Thus, the angled piece height H is also referred to as a louver height. Also, the angled piece height and the louver height H includes a thickness of the flat section 2a. The efficiency of heat exchange is determined based on the product of the coefficient of heat exchange and an area of heat transfer.

As shown in FIGS. 7 and 8, the efficiency of heat exchange improves when the louver pitch P is in a range between equal to or greater than 0.04 mm and equal to or less than 0.75 mm and the louver height H is in a range between equal to or greater than 0.02 mm and equal to or less than 0.4 mm.

Further, the efficiency of heat exchange further improves when the louver pitch P is in a range between equal to or greater than 0.2 mm and equal to or less than 0.7 mm and the louver height H is in a range between equal to or greater than 0.1 mm and equal to or less than 0.35 mm. Furthermore, the efficiency of heat exchange further improves when the louver pitch P is in a range between equal to or greater than 0.4 mm and equal to or less than 0.6 mm and when the louver height H is in a range between equal to or greater than 0.2 mm and equal to or less than 0.3 mm.

Second Embodiment

A second embodiment will be described with reference to FIG. 9. Hereafter, like components are denoted by like reference characters and a description thereof is not repeated.

In each flat section 2a, the louvers 20 are arranged with respect to the air flow direction A1 and symmetric with respect to a predetermined reference point C. Thus, the louvers 20 of the upstream group and the louvers 20 of the downstream group are arranged symmetrically. Hereafter, the louvers 20 of the upstream group are referred to as upstream louvers 20, and the louvers 20 of the downstream group are referred to as downstream louvers 20.

FIG. 9 shows some of the upstream louvers 20. In this embodiment, the angled pieces 2c of the upstream louvers 20 have different length, as shown in FIG. 9. Specifically, the upstream louver 20 has an upstream angled piece 21c on its upstream side and a downstream angled piece 22c on its downstream side with respect to the air flow direction A1. A height H1 of the upstream angled piece 21c is greater than a height H2 of the downstream angled piece 22c.

As such, since the upstream louvers 20 has the upstream angled pieces 21c that are higher than that of the other angled pieces 2c, the flow of the air is further disturbed on an upstream area of the flat section 2a. With this, the coefficient of heat transfer improves. Also, an increase of pressure loss (resistance to flow of the air) in a downstream area of the flat section 2a due to excess disturbance of the air is restricted.

In a case that upstream angled pieces 2c of the downstream louvers 20 are increased, the efficiency of heat exchange will be deteriorated. That is, in this case, because the number of the remaining louvers 20 with respect to the air flow direction A1 is small, the amount of heat exchange reduces due to an increase of pressure loss (resistance to flow of the air), as compared with the increase of the coefficient of heat exchange due to the disturbing effect.

In this embodiment, the upstream louvers 20 and the downstream louvers 20 have symmetric relationship. Since the height H1 of the upstream angled pieces 21c of the upstream louvers 20 is increased, the upstream louvers 20 and the downstream louvers 20 are not perfectly symmetric. However, the upstream louvers 20 and the downstream louvers 20 have the substantially U-shaped cross-sections, and hence are substantially symmetric. The above symmetric relationship include this substantially symmetric relationship.

Also, in this embodiment, the number of the upstream louvers 20 is equal to the number of the downstream louvers 20. However, the number of the upstream louvers 20 may be slightly different from the number of the downstream louvers 20 (e.g., one). The above symmetric relationship even includes this case. Also in first embodiment, the number of louvers 20 of the upstream group Gr1 may be different from the number of louvers 20 of the downstream group Gr2.

Also in this embodiment, since the louvers 20 are arranged in the symmetric relationship with respect to the reference point C, the bending forces are continuously exerted to the fin material 11 in directions canceling to each other in the fin forming step. Therefore, it is less likely that the fin material 11 will be deformed to be biased in one direction when the angled pieces 2c are bent. As such, the base pieces 2d and the angled pieces 2c are stably, evenly formed. Accordingly, the productivity of the fins 2 further improves.

Third Embodiment

A third embodiment will be described. The third embodiment is also shown in FIG. 9. Each flat section 2a has the upstream louvers 20 and the downstream louvers 20. Here, the downstream louvers 20 have the same shape as the louvers 20 of the first embodiment.

As shown in FIG. 9, the upstream louvers 20 have the upstream angled pieces 21c and the downstream angled pieces 22c, and the height H1 of the upstream angled pieces 21c is higher than the height H2 of the downstream angled pieces 22c.

In the downstream louvers 20, the upstream angled pieces 2c and the downstream angled pieces 2c have the same height H. Thus, the upstream louvers 20 have the height higher than that of the downstream louvers 20. In this embodiment, the heights H, H1, H2 have the relationship of H1>H>H2. Further, the height H and the height H2 can be substantially equal. Alternatively, the heights H, H1, H2 can have the relationship of H1+H2>2×H.

As such, since the flow of the air is further disturbed by the upstream angled pieces 21c having the height larger than the other, the coefficient of heat transfer is increased. Also, since it is less likely that the flow of the air will be excessively disturbed in the downstream area of the flat section 2a, the increase of pressure loss (resistance to flow of the air) is suppressed.

In a case that the height of the upstream angled pieces 2c of the downstream louvers 20 are increased, the efficiency of heat exchange will be reduced. That is, in this case, because the number of the remaining louvers 20 with respect to the air flow direction A1 is small, the amount of heat exchange reduces due to an increase of pressure loss (resistance to flow of the air), as compared with the increase of the coefficient of heat exchange due to the disturbing effect.

Also, only one of or some of the upstream louvers 20 may have the upstream angled pieces 21c having the height H1 larger than the height H of the downstream louvers 20. Further, the height of the upstream louvers 20 may be increased larger than the height of the downstream louvers 20 in average.

In this embodiment, since the upstream angled pieces 21c and the downstream angled pieces 22c have the different heights, the upstream louvers 20 and the downstream louvers 20 are not perfectly symmetric. However, the upstream louvers 20 and the downstream louvers 20 similarly have the substantially U-shaped cross-section. Thus, the upstream louvers 20 and the downstream louvers 20 still have the symmetric relationship.

Also, even when the number of the upstream louvers 20 and the number of the downstream louvers 20 may be slightly different, the upstream louvers 20 and the downstream louvers 20 still have the symmetric relationship.

Fourth Embodiment

A fourth embodiment will be described with reference to FIGS. 10 to 12. In this embodiment, the height H1 of the upstream angled piece 21c is in a range between equal to or greater than 0.02 mm and equal to or less than 0.4 mm. Also, the louver pitch P is in a range between equal to or greater than 0.02 mm and equal to or less than 0.75 mm. Further, the height H2 of the downstream angled piece 22c is equal to the height H1 of the upstream angled piece 21c.

Since the angled pieces 2c are bent from the flat section 2a, the width L of the base piece 2d of the louver 20 varies in accordance with the height H1 of the upstream angled piece 21c and the louver pitch P. FIG. 11 shows a relationship between a louver ratio H1/L and the efficiency of heat exchange. The louver ratio H1/L is a ratio of the height H1 of the upstream angled piece 21c to the width L of the base piece 2d. As shown in FIG. 11, when the louver ratio H1/L is in a range between equal to or greater than 0.9 and equal to or less than 1.25, the efficiency of heat exchange is sufficient.

FIG. 12 shows a relationship between the louver ratio H1/L and the pressure loss. When the louver ratio H1/L is equal to or smaller than 1.2, the pressure loss is reduced.

Considering the efficiency of heat exchange and the pressure loss, it is preferable that the louver ratio H1/L is in the range equal to or greater than 0.9 and equal to or less than 1.25. More preferably, the louver ratio H1/L is in a range between equal to or greater than 0.95 and equal to or less than 1.2. Still more preferably, the louver ratio H1/L is in a range between equal to or greater than 1.0 and equal to or less than 1.15.

Fifth Embodiment

A fifth embodiment will be described with reference to FIGS. 13A to 14C. In the above embodiment, the angled pieces 2c are right-angled relative to the flat section 2a to improve the efficiency of heat exchange. However, the angle of the angled pieces 2c relative to the flat section 2a is not limited to the right angle, but may be modified as long as the flow of the air is disturbed.

In this embodiment, the angle of the angled pieces 2c relative to the flat section 2a is modified in a range between equal to or greater than 40° and equal to or less than 140°, for example. Therefore, the cross-sectional shape of the louvers 20 is not limited to the substantially U-shape, but are any other shapes. Here, the angle of each angled piece 2c is defined relative to the flat section 2a, i.e., relative to a state before it is bent from the flat section 2a. Thus, the angle is also referred to as a bending angle.

FIGS. 13A to 13C shows examples in which the angles of the angled pieces 2c are modified in variable ways. In FIG. 13A, the upstream and downstream angled pieces 2c are angled approximately 40°, respectively. In FIG. 13B, the upstream and downstream angled pieces 2c are angled approximately 140°, respectively. In FIG. 13C, the upstream angled pieces 21c are angled approximately 90°, and the downstream angled pieces 22c are angled approximately 40°.

The shape of the louvers 20 are further modified. FIGS. 14A to 14C show examples of the shapes of the louvers 20. In FIG. 14A, the angled piece 2c and a connecting portion between the angled piece 2c and the base piece 2d are angled relative to the flat section 2a. In FIG. 14B, the angled pieces 2c are formed such that the base piece 2d and the angled pieces 2c share a smooth curved wall having an arc shape in cross-section.

In FIG. 14C, an end of the upstream angled piece 21c is bent toward an upstream position with respect to the air flow direction A1, and an end of the downstream angled piece 22c is bent toward a downstream position with respect to the air flow direction A1.

Accordingly, the shape of the louvers 20 is not limited to the illustrated shapes as long as the flow of the air along the flat section 2a is disturbed.

In the above embodiments, the present invention is employed in the radiator of the vehicle air conditioner, but may be employed in any other heat exchangers such as a heater core of a vehicle air conditioner, evaporator or condenser of a vapor compression refrigerating cycle, a radiator for cooling engine cooling water.

The shape of the fins 2 is not limited to the corrugated shape. The fins 2 may be other fins such as plate fins having flat walls, and pin fins having the shape of pin. The louvers 20 may be arranged in plural rows in each flat section 2a in the air flow direction A1. Further, the angled pieces 2c may be inclined at a predetermined angle relative to a direction perpendicular to the air flow direction A1. Moreover, the number of the louvers 20 may be different in plural flat sections 2a. Also, the flat section 2a may have only one louver 20. Moreover, the above embodiments may be implemented in variable combinations.

The example embodiments of the present invention are described above. However, the present invention is not limited to the above example embodiment, but may be implemented in other ways without departing from the spirit of the invention.